Generator Sizing Calculator — for Canadian Homes

Estimate standby generator kW from essential residential loads. Service conductors still require separate Rule 8-200 and 4-004 sizing.

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By using this calculator you agree to our Terms. This tool does not provide authoritative or binding interpretations of CSA requirements. All values must be verified by a qualified professional and approved by the Authority Having Jurisdiction (AHJ).

Calculations aligned with CE Code 2024 · Standby load & demand methods · CE Code 2024. Verify adopted edition and local amendments with your AHJ.

How generator sizing works

Select essential loads above; the calculator applies demand factors and recommends generator size.

Select essential loads

Choose heating, refrigeration, lighting, pumps, and other circuits that must run during an outage. Exclude non-essential loads to keep generator size practical.

Apply demand factors

Not all loads run at full nameplate simultaneously. The calculator applies residential demand methods to estimate realistic standby kW.

Motor starting margin

Add margin for motor inrush on pumps and compressors. Compare results to generator nameplate kW or kVA and transfer switch ratings.

Pair with service sizing

Generator sizing is separate from service conductor sizing. Use the residential load calculator and conductor sizer for the permanent service.

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Frequently asked questions

How do I size a standby generator for a Canadian home?
List essential loads (heat, refrigeration, lighting, sump, selected circuits), apply demand factors, add motor starting margin where needed, and compare to generator nameplate kW or kVA.
What loads should run on a standby generator?
Typically heating controls, refrigeration, critical lighting, sump pumps, and selected receptacle circuits. Non-essential loads are often excluded to keep generator size practical.
Does generator sizing use CE Code load calculations?
Standby generator sizing uses load enumeration and demand methods aligned with residential practice. Service conductors still require Rule 8-200 and Rule 4-004 sizing separately.
How much margin should I add?
Many designers add 15–25% margin for motor starting and future load growth. Confirm with generator manufacturer loading guidelines and transfer equipment ratings.

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